With respect to LEDs due to the increasing requirements it is noted in the recent years that there is a change from the classical blue LED to the so-called “GaN-on-GaN” or “n-Pola”, “non-polar” or “semi-polar” technologies which are able to operate at higher current densities and to generate a significantly higher luminous efficiency/output therefrom. In order to generate visible radiation, in particular (warm) white light, moreover, corresponding converter materials are required which convert the UV-A or blue primary radiation generated by the semiconductor chip in such a way that light of the respective color can be generated.
As an alternative to the abovementioned LED technology other LED technologies are also considered which are capable of generating particularly high radiation powers by realizing higher electrical currents per mm2 of light-emitting surface, such as the LED technologies referred to as “3D”-LED or Nano-LED or Nanowire-LED technologies.
Alternatively, solutions based on laser technology are taken into consideration, too, i.e. in which the UV-A or blue primary radiation is generated by means of lasers.
When a blue LED is used in combination with a yellow fluorescent material, (cold) white light can be generated whose color rendering index is comparatively low. In order to achieve a high color rendering index use of an RGB system is necessary, wherein in the case of a blue emitting semiconductor element a green and a red emitting, and in the case of a UV-A emitting semiconductor element a blue, a green or yellow and a red emitting fluorescent material are necessary.
These new techniques, in particular the n-Pola technique, are usually used with the existing converter materials, this, however, has the disadvantage that due to the mostly high saturation associated with these converter materials, in particular regarding red emitting converter materials, the advantages of the n-Pola technique cannot be optimally utilized.